Adding Genesis/MD to MC-Cthulhu

So, about a year ago I had been working on a plan for a universal arcade stick with support for a bunch of retro consoles plus PC and PS3 (via an MC-Cthulhu board), Sega Genesis / Mega Drive via a padhacked 6-button pad from eBay and Xbox 360 via a leftover control board from one of my Mad Catz sticks.

360 and Cthulhu were supposed to share the same USB-over-RJ45 with a toggle switch to go between them and Genesis/MD was going to have a little pigtail that could hook up to an extension cable when needed. When I got the 360 board wired into the Cthulhu, though, everything went haywire with phantom button presses and all sorts of nonsense. This got me pretty bummed out about the whole project and I put it on ice.

However, there's been a lot of interest over on my MC-Cthulhu pinout page from people trying to integrate Genesis/MD input with the Cthulhu board since then, so I figured I'd better at least finish up that part and report my experience, which I finally did last night.

I won't go into a ton of detail in this post, as the "how" bits have already been covered in my other posts (linked above), so instead I'll focus on what worked and what didn't.

First off, I had originally tried swapping between the Cthulhu and the 360 board (before I abandoned it) using a momentary DPDT switch like you find on a guitar foot pedal. I wanted something tough that was hard to press, so it wouldn't trigger accidentally mid-game. This ended up being the wrong tool for the job, though, as it only switched to the other board while the switch was actually held down. So, I switched over to an ON/ON DPDT 2-position switch. I'm pretty confident this would have worked as intended had my 360 board wanted to cooperate.

The way the switch is supposed to work is: from your USB, you have 4 lines--GND, 5v, Data+ and Data-. The 5v and GND are wired onto the extra solder points on the Cthulhu (that is, the 3 sets of thru-holes where you solder on the RJ45 lines) and the Data+/- lines are wired onto the switch, with 2 coming from the Cthulhu and 2 coming the 360 board's USB header. The output lines from the switch (typically the 2 center leads) connect to the RJ45 lines. In normal use, both boards will be powered (whenever you do a multi-board solution, all boards need their voltage and ground lines connected together at all times) but the one that actually sends/receives data will be controlled by the toggle switch.

Once I got the boards wired together and noticed the strange behavior, I did a lot of troubleshooting and determined that just having the 5v and GND lines linked up was enough to break everything, so that was that. I may revisit it another time with a different 360 board, but for now I decided to just drop 360 support altogether. With the 360 board out of the picture, I didn't need the switch anymore, but I just left it on there anyway rather than having a gaping hole in the side of my stick for dust and liquids to sneak in. Plus, now I have a little fidget thingie I can fiddle with between matches.

sorry for blurry pic :(

Moving on to the Genesis/MD pad, there wasn't really anything unexpected. I soldered the padhack's button lines to the secondary soldering points on the Cthulhu (the 2 rows of thru-holes labeled A-H and 1-9) as outlined at the end of my pinout post and it all works great. The crummy pad I used has a very short cable, which made it super-easy to cram into my already-crowded Mad Catz SE chassis.

Yes, the wiring is a mess. Good thing nobody ever sees it but me (and now you)

You'll notice I did a little loop around a screw post before sending the connector out the back side. That's to prevent the wire from tugging on the pad PCB and ripping out my solder joints. I also covered the entire PCB and solder points with electrical tape to prevent any stray grounding/bridging.

The pigtail. It's pretty unobtrusive without the extension cable attached

You might also notice that I removed the 360 home/LED/turbo panel with a 3D-printed blank, which just barely fits a 24 mm button to serve as the Cthulhu's HOME button.

While I was at it, I took a tip from u/gongfuren on reddit's r/fightsticks board and swapped out some plungers on my short-stem IL competition buttons for a cool "bullseye" look and also removed the springs from the buttons, which gives them a much lighter touch. They're still a lot stiffer than Sanwa buttons (which is good, IMO, as I like to rest my hands on the buttons) but they feel significantly more responsive than with the spring, and they still keep their satisfying cherry click.

Here's the final result:

And here's my other IL stick that I swapped plungers with: